This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 56 |
| 5 | 7100 |
| 6 | 252792 |
| 7 | 3378942 |
| 8 | 26249184 |
| 9 | 144455454 |
| 10 | 625745100 |
| 11 | 2271361422 |
| 12 | 7192874328 |
| 13 | 20427662398 |
| 14 | 53065637212 |
| 15 | 127956238350 |
| 16 | 289628321664 |
| 17 | 620834113614 |
| 18 | 1269178026012 |
| 19 | 2488676915070 |
| 20 | 4702895069400 |
| 21 | 8598589878606 |
| 22 | 15261688799500 |
| 23 | 26371002575326 |